The present invention relates to a method for producing a starting material for polycarbonate resin and to a method for producing polycarbonate resin. More precisely, the invention relates to an inexpensive and simple method for producing a starting material for polycarbonate resin and for producing polycarbonate resin.
Polycarbonate resin is a type of engineering plastics having well-balanced transparency, heat resistance and mechanical strength, and is used in many fields. Based on its overall characteristics of transparency, heat resistance, hydrolysis resistance and dimensional stability, polycarbonate resin is especially much used these days for raw materials for optical recording media such as compact discs, laser discs, optical memory cards, optical discs, digital video discs, etc. Polycarbonate resin of high transparency suitable to optical appliances including such optical recording media is produced through interfacial polymerization.
For producing polycarbonate resin through interfacial polymerization, generally employed is a method of reacting a bisphenol compound with phosgene. in the presence of an organic solvent and an aqueous alkali solution. For this, it is well known that a granulated solid bisphenol compound, which serves as the essential starting material for polycarbonate resin, is dissolved in an aqueous alkali solution and phosgene gas is introduced into the resulting solution.
The bisphenol compound, which is the essential starting material for polycarbonate resin, is granulated in a complicated process. For example, 2,2-bis(4-hydroxyphenyl)propane is, after produced through reaction of phenol with acetone, purified in many steps and then granulated in the final step. For granulating the bisphenol compound, used is a granulator such as a spray drier or the like, in which the bisphenol compound is formed into liquid drops and then cooled and solidified.
For producing polycarbonate resin from the bisphenol compound through interfacial polymerization, solid grains of the bisphenol compound having been solidified and granulated in the process as above are dissolved in an aqueous alkali solution, and the resulting solution is used in polycondensation.
The process for producing the bisphenol compound that serves as a starting material in producing polycarbonate resin through interfacial polymerization, and the process for producing polycarbonate resin require complicated many steps as in the above, and are therefore problematic in that many plants and much labor are needed and the production costs are high.
The present invention is to provide an inexpensive and simple method for producing a starting material for polycarbonate resin and for producing polycarbonate resin.
We, the present inventors have assiduously studied to solve the problems noted above, and, as a result, have found that, in a process for producing polycarbonate resin through interfacial polymerization, (I) when a bisphenol compound prepared in melt in a process of bisphenol compound production is, without being granulated, directly mixed in an aqueous alkali solution while it is in melt, and when the thus-prepared aqueous alkali solution of the bisphenol compound is used as the starting material for polycarbonate resin production, or (II) when a bisphenol compound prepared in melt in a process of bisphenol compound production is, without being solidified, directly mixed with water to be in liquid at a temperature not higher than the melting point of the bisphenol compound, and then dissolved in an aqueous alkali solution, and when the thus-prepared aqueous alkali solution of the bisphenol compound is used as the starting material for polycarbonate resin production through interfacial polymerization, then the above-mentioned object can be attained. On the basis of these findings, we have completed the present invention (including first and second aspects).
Specifically, the invention is summarized as follows:
I. First Aspect of the Invention
(1) A method for producing a starting material for polycarbonate resin production through interfacial polymerization, which is characterized in that a bisphenol compound prepared in melt in a process of bisphenol compound production is mixed and dissolved in an aqueous alkali solution at 20 to 80xc2x0 C.
(2) The method for producing a starting material for polycarbonate resin of above (1), wherein the bisphenol compound includes bis(4-hydroxyphenyl)alkanes.
(3) A method for producing polycarbonate resin, which is characterized in that a bisphenol compound prepared in melt in a process of bisphenol compound production is mixed and dissolved in an aqueous alkali solution at 20 to 80xc2x0 C, and the resulting aqueous alkali solution of the bisphenol compound is used as the starting material for polycarbonate resin production through interfacial polymerization.
II. Second Aspect of the Invention
(1) A method for producing a starting material for polycarbonate resin, which is characterized in that a bisphenol compound prepared in melt in a process of bisphenol compound production is, without being solidified, directly mixed with water to be in liquid at a temperature not higher than the melting point of the bisphenol compound, and then dissolved in an aqueous alkali solution.
(2) The method for producing a starting material for polycarbonate resin of above (1), wherein the bisphenol compound includes bis(4-hydroxyphenyl)alkanes.
(3) A method for producing polycarbonate resin, which is characterized in that a bisphenol compound prepared in melt in a process of bisphenol compound production is, without being solidified, directly mixed with water to be in liquid at a temperature not higher than the melting point of the bisphenol compound, and then dissolved in an aqueous alkali solution, and the resulting aqueous alkali solution of the bisphenol compound is used as the starting material for polycarbonate resin production through interfacial polymerization.
Modes of carrying out the invention are described hereinunder.
I. First Aspect of the Invention
In this section, the first aspect of the invention will be simply referred to as the invention.
In the method of the invention for producing a starting material for polycarbonate resin production through interfacial polymerization, a bisphenol compound prepared in melt in a process of bisphenol compound production is mixed and dissolved in an aqueous alkali solution at 20 to 80xc2x0C; and, in the method of the invention for producing polycarbonate resin, the resulting aqueous alkali solution of the bisphenol compound is used as the starting material for polycarbonate resin production.
In the method of the invention, the step of polycarbonate resin production through interfacial polymerization is per-se known. It comprises adding phosgene to the aqueous alkali solution of a bisphenol compound, with stirring it in the presence of an organic solvent such as methylene chloride or the like capable of well dissolving polycarbonate resin, to thereby form a polycarbonate oligomer having a chloroformate terminal, followed by further polymerizing the oligomer.
The bisphenol compound that serves as the essential starting material in the polycarbonate resin production includes, for example, 4,4xe2x80x2-dihydroxybiphenyls such as 4,4xe2x80x2-dihydroxybiphenyl, 3,3xe2x80x2-difluoro-4,4xe2x80x2-dihydroxybiphenyl, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dimethyldiphenyl, 4,4xe2x80x2-dihydroxy-2,2xe2x80x2-dimethylbiphenyl, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dicyclohexylbiphenyl, etc.; bis(4-hydroxyphenyl)methanes such as bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)diphenylmethane, bis(4-hydroxyphenyl)phenylmethane, bis(3-methyl-4-hydroxyphenyl)methane, bis(3-nonyl-4-hydroxyphenyl)methane, bis(3,5-dimethyl-4-hydroxyphenyl)methane, bis(3,5-dibromo-4-hydroxyphenyl)methane, bis(3-chloro-4-hydroxyphenyl)methane, bis(3-fluoro-4-hydroxyphenyl)methane, bis(2-tert-butyl-4-hydroxyphenyl)phenylmethane,; bis(2-hydroxyphenyl)methanes such as bis(2-hydroxyphenyl)methane, 2-hydroxyphenyl-4-hydroxyphenylmethane, bis(2-hydroxy-4-methylphenyl)methane, bis(2-hydroxy-4-methyl-6-tert-butylphenyl)methane, bis(2-hydroxy-4,6-dimethylphenyl)methane, etc.; bis(4-hydroxyphenyl)ethanes such as 1,1-bis(4-hydroxyphenyl)ethane, 1,2-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl-1-phenylethane, 1,1-bis(4-hydroxy-3-methylphenyl)-1-phenylethane, 1,1-bis(4-hydroxy-3-methylphenyl)-1-phenylethane, 2-(4-hydroxy-3-methylphenyl)-2-(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(2-tert-butyl-4-hydroxy-3-methylphenyl)ethane, 1-phenyl-1,1-bis(3-fluoro-4-hydroxyphenyl)ethane,; bis(2-hydroxyphenyl)ethanes such as 1,1-bis(2-hydroxy-4-methylphenyl)ethane, etc.; bis(4-hydroxyphenyl)propanes such as 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)propane, 2,2-bis(2-methyl-4-hydroxyphenyl)propane, 2,2-bis(3-methyl4-hydroxyphenyl)propane, 2,2-bis(3-isopropyl-4-hydroxyphenyl)propane, 2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane, 2,2-bis(3-phenyl-4-hydroxyphenyl)propane, 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 2,2-bis(3-fluoro-4-hydroxyphenyl)propane, 2,2-bis(3-bromo-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-difluorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(3-bromo-4-hydroxy-5-chlorophenyl)propane, 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane,; bis(2-hydroxyphenyl)propanes such as 2,2-bis(2-hydroxy-4-sec-butylphenyl)propane, 2,2-bis(2-hydroxy-4,6-dimethylphenyl)propane, etc.; bis(4-hydroxyphenyl)butanes such as 2,2-bis (4-hydroxyphenyl)butane, 2,2-(3-methyl-4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)-2-methylpropane, 1,1-bis(2-butyl-4-hydroxy-5-methylphenyl)butane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)butane, 1,1-bis(2-methyl-4-hydroxy5-tert-pentylphenyl)butane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)butane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)butane, 2,2-bis(4-hydroxyphenyl)-3-methylbutane, 1,1-bis (4-hydroxyphenyl)-3-methylbutane, etc.; bis(hydroxyphenyl)alkanes such as 3,3-bis(4-hydroxyphenyl)pentane, 2,2-bis(4-hydroxyphenyl)hexane, 2,2,-bis(4-hydroxyphenyl)heptane, 2,2-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)heptane, 2,2-bis(4-hydroxyphenyl)octane, 2,2-bis(4-hydroxyphenyl)nonane, 2,2-bis(4-hydroxyphenyl)decane, 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxy-3,5-dimethylphenyl)cyclohexane, 1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3-phenyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(3-methyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, etc.; bis(4-hydroxyphenyl)ethers such as bis(4-hydroxyphenyl)ether, bis(3-fluoro-4-hydroxyphenyl)ether, etc.; bis(4-hydroxyphenyl)sulfides such as bis(4-hydroxyphenyl)sulfide, bis(3-methyl-4-hydroxyphenyl)sulfide, etc.; bis (4-hydroxyphenyl)sulfoxides such as bis(4-hydroxyphenyl)sulfoxide, bis(3-methyl-4-hydroxyphenyl)sulfoxide, etc.; bis (4-hydroxyphenyl)sulfones such as bis(4-hydroxyphenyl)sulfone, bis(3-methyl-4-hydroxyphenyl)sulfone, bis(3-phenyl-4-hydroxyphenyl)sulfone, etc.; bis(4-hydroxyphenyl)ketones such as 4,4xe2x80x2-dihydroxybenzophenone, etc.; bis(hydroxyphenyl)fluorenes such as 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(3-methyl4-hydroxyphenyl)fluorene, 9,9-bis(3-phenyl-4-hydroxyphenyl)fluorene, etc.; dihydroxy-p-terphenyls such as 4,4xe2x80x2-dihydroxy-p-terphenyl, etc.; bis(hydroxyphenyl)pyrazines such as 2,5-bis(4-hydroxyphenyl)pyrazine, 2,5-bis(4-hydroxyphenyl)-3,6-dimethylpyrazine, 2,5-bis(4-hydroxyphenyl)-2,6-diethylpyrazine, etc.; bis(hydroxyphenyl)menthanes such as 1,8-bis(4-hydroxyphenyl)menthane, 2,8-bis(4-hydroxyphenyl)menthane, 1,8-bis(3-methyl-4-hydroxyphenyl)menthane, 1,8-bis(4-hydroxy-3,5-dimethylphenyl)menthane,etc.; bis[2-(4-hydroxyphenyl)-2-propyl]benzenes such as 1,4-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, etc.; dihydroxynaphthalenes such as 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, etc.; dihydroxybenzenes such as resorcinol, hydroquinone, catechol, etc.
Of those bisphenols, especially preferred are bis(4-hydroxyphenyl)alkanes, as the polycarbonate resins having started from them have well balanced physical properties of transparency, heat resistance, hydrolysis resistance and dimensional stability, and are favorable to materials for optical appliances.
Regarding the production of the bisphenols, for example, 2,2-bis(4-hydroxyphenyl)propane is produced by reacting acetone with phenol in the presence of a catalyst. For the catalyst, for example, preferred are sulfonic acid-type cation-exchange resins such as sulfonated styrene-divinylbenzene copolymers, sulfonated crosslinked styrene polymers, phenol-formaldehyde-sulfonic acid resins, benzene-formaldehyde-sulfonic acid resins, etc. In the case, preferably used are alkylmercaptans serving as a catalyst promoter. Excess phenol over acetone is reacted with acetone.
The reaction mixture contains non-reacted phenol and acetone, the catalyst used and also side products such as water, alkylmercaptans, organic-sulfur compounds and coloring matters, in addition to the intended product, 2,2-bis(4hydroxyphenyl)propane. Therefore, the reaction mixture is subjected to distillation under reduced pressure to remove the non-reacted acetone, water and alkylmercaptans. Then, this is further subjected to distillation under reduced pressure to remove the non-reacted phenol, in the next step of concentrating the product, 2,2-bis(4-hydroxyphenyl)propane.
The concentrate residue obtained in the concentration step has a 2,2-bis(4-hydroxyphenyl)propane concentration of from 20 to 50% by weight, preferably from 20 to 40% by weight, and this is then cooled to 40 to 70xc2x0 C. in the next crystallization step, in which an adduct of 2,2-bis (4-hydroxyphenyl)propane and phenol (hereinafter referred to as a phenol adduct) is crystallized out in slurry. The concentrate residue slurry is then filtered or centrifuged whereby the phenol adduct crystal is separated from the mother liquid. The thus-obtained crystal, 2,2-bis(4-hydroxyphenyl)propane/phenol 1/1 adduct is heated and melted at 100 to 160xc2x0 C., and the resulting melt mixture is subjected to distillation under reduced pressure to remove phenol. Thus is obtained 2,2-bis(4-hydroxyphenyl)propane.
2,2-Bis(4-hydroxyphenyl)propane thus obtained is in melt. In general, this is formed into liquid drops, and then cooled and solidified into a granular product, in a granulator such as a spray drier or the like. Then, the resulting granular solid of 2,2-bis(4-hydroxyphenyl)propane is transported into an apparatus for polycarbonate resin production, in which this is dissolved in an aqueous alkali solution such as an aqueous sodium hydroxide solution or the like in the unit for preparing the starting material for polycarbonate resin, and the resulting solution is used for polycarbonate resin production.
In the present invention, the molten bisphenol such as 2,2-bis(4-hydroxyphenyl)propane prepared in the process as above is, without being solidified and granulated in the granulation step, directly dissolved in an aqueous alkali solution such as an aqueous sodium hydroxide solution or the like in the step of preparing the starting material for polycarbonate resin production. The invention is characterized by the direct preparation of the starting material for polycarbonate resin production. In the invention, the temperature of the aqueous alkali solution in which the bisphenol is dissolved is controlled to fall between 20 and 80xc2x0 C. If the temperature of the aqueous alkali solution is lower than 20xc2x0 C., a lot of time will be taken to dissolve the bisphenol in the solution, and the productivity of polycarbonate resin will be low. On the other hand, if the temperature is higher than 80xc2x0 C., the bisphenol will be thermally decomposed and discolored, and, in addition, the aqueous alkali solution will corrode the apparatus.
For mixing the molten bisphenol with such an aqueous alkali solution, for example, employed is a dissolution tank equipped with a line mixer or a stirrer. Preferably, the atmosphere in the apparatus is previously purged with an inert gas such as nitrogen gas or the like so that the mixing operation can be effected in such an inert gas atmosphere. The temperature of the molten bisphenol is not lower than the melting point of the bisphenol, but is preferably higher by at most 80xc2x0 C. than the melting point thereof. If the temperature of the bisphenol melt is higher than it, the bisphenol will be decomposed and discolored.
For the aqueous alkali solution in which the molten bisphenol is dissolved, preferred is sodium hydroxide. In place of sodium hydroxide, however, any other alkali metal hydroxides and alkaline earth metal hydroxides may also be employed. The concentration of the aqueous alkali solution may fall between 2 and 47% by weight. Preferably, the amount of the aqueous alkali solution to be used falls between 1.9 and 2.5 mols relative to one mol of the bisphenol to be dissolved in the solution. Regarding the reaction between bisphenol and alkali such as sodium hydroxide, one mol of bisphenol theoretically reacts with 2 mols of sodium hydroxide. In practical reaction, however, it is desirable that the amount of sodium hydroxide is excessive in some degree over bisphenol.
When the molten bisphenol is mixed with such an aqueous alkali solution, a reducing agent is preferably added thereto. The reducing agent may be any ordinary one. For example, preferred are sodium sulfite, sodium thiosulfate, sodium dithionite (hydrosulfite), etc. Its amount may fall between 10 and 1,000 ppm by weight of the aqueous alkali solution. The reducing agent may be added to the aqueous alkali solution before bisphenol is added to the solution, or may be added to water which is used for controlling the alkali concentration of the solution, or may be added to the aqueous alkali solution simultaneously with molten bisphenol added thereto. The reducing agent added improves the color tone of the polycarbonate resin that starts from the aqueous alkali solution of bisphenol obtained herein.
The method of the invention for producing polycarbonate that starts from the aqueous alkali solution of bisphenol compound prepared in the manner as above may be the same as that for conventional polycarbonate resin production through interfacial polymerization, except that it does not require the step of dissolving solid grains of bisphenol compound in an aqueous alkaline solution.
For example, phosgene is added to the aqueous alkali solution of bisphenol compound, with stirring it in the presence of an organic solvent such as methylene chloride or the like capable of well dissolving polycarbonate resin, to thereby form a polycarbonate oligomer having a chloroformate terminal, and the oligomer is further polymerized. The polycondensation condition, the catalyst, the mode of molecular weight control and the additives to be optionally added for the method may be the same as those for conventional methods.